1. Field of the Invention
The present invention relates to a method for mounting a belt which can expand and contract on a pair of pulleys, an apparatus for mounting the belt on the pulleys, a method for mounting and dismounting the belt to and from the pulleys, and an apparatus for mounting and dismounting the belt to and from the pulleys.
2. Discussion of the Related Art
In a belt driving unit, a V-ribbed belt is wound around a pulley (driving pulley) having a pulley groove on an outer periphery thereof. On this type of belt driving mechanism, a tension adjusting member such as a tension pulley is generally provided. After the V-ribbed belt is mounted on the driving pulley, the tension adjusting member is properly set for imparting a predetermined tension to the belt.
On the other hand, there is another belt driving mechanism without a tension adjusting member. Such belt driving mechanism was designed for simplifying the structure and decreasing the cost. For this mechanism, a V-ribbed belt which expands and contracts in the lengthwise direction of the belt (stretchable V-ribbed belt) is used. The belt is positioned on the pulleys by the installation across the flange of the pulley. The belt includes a flat main body in the form of a ring, wherein core wires made of fabrics having good stretching properties are embedded. The main body has an inner periphery having a plurality of V-ribs which are integral with each other. The V-ribs stretch in the peripheral direction of the belt main body.
On the other hand, the pulley has a pulley groove including a plurality of pulley V-grooves extending in a peripheral direction of the pulley. The plurality of V-ribs is configured to fit into the pulley V-grooves prepared on the pulley.
When the V-ribbed belt is seated on the pulley, it is necessary to stretch the belt in a peripheral direction of the belt. The stretched belt is seated in the pulley groove from the outer side of the flange, with respect to the axial direction of the pulley. For this operation, a large tensile strength generates, that requires the use of an apparatus for mounting a belt on a pulley.
FIG. 25 is a diagram for showing an apparatus for mounting a striated belt on a pulley disclosed in U.S. Pat. No. 6,033,331. A belt mounting apparatus 101 includes a conical member 103 provided with a smooth guiding surface 104, a guiding element 105, a leg 106, a top part 102 and a lever 107. The leg 106 of the apparatus 101 has an inner periphery which is slidable on a pulley flange 111 provided on the pulley 110. An end of the lever 107 engages with the top part 102.
The leg 106 and the conical member 103 of the apparatus 101 are brought into contact with the outer periphery of the pulley flange 111. Further, a ribbed belt 120 is seated on the pulley groove 113 at a rear part of the apparatus 101 with respect to the rotational direction thereof, as shown by the arrow in FIG. 25. Then, the ribbed belt 120 is positioned so as to extend with contacting the conical member 103, smooth guiding surface 104, and guiding element 105. The conical member 103 has functions (i) to prevent the thus provided ribbed belt 120 from being detached from the pulley groove 113, and (ii) to have the extending direction of the ribbed belt 120 changed from the outer side of the pulley to a direction along the pulley groove 111.
When the V-ribbed belt 120 is set as described above, the lever 107 is operated so that the leg 106 is pressed against the outer periphery of the pulley flange 111. By this operation, the belt installation apparatus 101 rotates in the direction of periphery of the pulley 110. Accordingly, a rear part of the V-ribbed belt 120 with respect to the rotational direction of the apparatus 101 is gradually seated in the pulley groove 113. Consequently, the V-ribbed belt 110 is completely mounted on the pulley 110.
It is possible, however, the apparatus 101 disclosed in U.S. Pat. No. 6,033,331 gives a damage on the pulley 110 when the leg 106 are brought into pressure contact with and slides on the pulley flange 111.
Moreover, there is a difficulty to use the apparatus 101 disclosed in the U.S. Pat. No. 6,033,331 for mounting a V-ribbed belt on a pulley having an outer pulley groove and an inner pulley groove in parallel on the outer periphery of the pulley. More precisely, the belt is positioned in the inner pulley groove by passing over the outer pulley. In this case, the V-ribbed belt 120 is stretched with a large deformation of the belt 120 by the guidance of the guiding surface 104. Namely, the belt 120 is brought into a pressure contact with the smooth guiding surface 104 and the leg 106. Accordingly, the V-ribbed belt 120 and the pulley could be damaged during the mounting operation.
On the other hand, it is possible that the V-ribbed belt is provisionally positioned on the outer pulley groove, and then to be moved to the inner pulley groove. In this case, the belt once placed on the outer pulley groove has to be held by a hand for the relocation. For this purpose, the V-ribbed belt on the outer pulley groove is stretched in the axial direction of the pulley, with the ribbed belt being twisted. At the same time, the pulley is rotated so that the pulley is transferred to the inner pulley groove. During this operation, the belt is forced to move across the plurality of grooves on the outer pulley groove, a pulley flange formed between the outer pulley groove and the inner pulley groove, and the plurality of grooves formed in the inner pulley groove. Therefore, the ribbed belt and the pulley would be damaged by being scratched. Further, there is such a possibility that an operator pinches his finger between the pulley and the V-ribbed belt. Moreover, this operation requires to rotate the pulley 2 or 3 times for assembly, that would be resulting in a low operational efficiency.